The profitability of an airline is directly related to the number of passengers and the amount of cargo-carrying space its planes are equipped to transport. The greater the passenger seating space, the greater the potential passenger revenues. Similarly, the greater the cargo-carrying space, the greater are the potential cargo revenues. Therefore, an airline can increase its profitability by increasing passenger seating space and cargo-carrying capability.
One method of increasing airplane passenger and cargo space is to increase the length of the craft's fuselage. This process is commonly known as "stretching". There are a number of problems associated with stretching an airplane, including a reduction in the aft body rotation clearance, disproportionate growth of the lower cargo space, a reduction in airplane maneuverability in and around airports, and a reduction in the ability to park the aircraft in length-constrained airport gates.
A second method of increasing passenger and cargo space is to use a full length main seating deck and an additional upper seating deck provided either over the entire length of the fuselage, over a forward upper area, or over an aft upper area. Increasing passenger space by use of a forward, an aft, or a full upper deck is generally preferred to stretching an aircraft because the resulting airplane is easier to maneuver at airports and is capable of larger rotation angles during takeoff and landing. Such a craft also has reduced fuselage wetted area per seat and hence reduced skin friction drag on a per seat basis.
There are a number of problems associated with attempting to design a viable full upper deck airplane. One problem is that it is difficult to design a large airplane with a full upper deck that includes non-conflicting escape routes from both the main and upper decks. For a full upper deck or cabin airplane configuration, a sufficient number of doors fitted with deployable escape slides must be provided on the upper deck as well as on the main deck, in order to allow all passengers to quickly exit the plane during an emergency situation. These doors must be spaced no more than sixty feet apart longitudinally in order to meet United States Federal Aviation Regulations. In many cases, there will be a resulting high risk that upper deck slides, while deploying or deployed, are impacted by or otherwise conflict with nearby lower deck slides and/or with the wing of the airplane. This becomes a particularly challenging issue for a large airplane configuration with a long root chord, low wing. Another problem in designing a viable full upper deck configuration, is that dual deck craft have distributions of area-rule cross-sectional area verses longitudinal position that are significantly non-optimal. Thus, full upper deck configurations typically suffer from relatively high levels of transonic drag.
Accordingly, a need exists for an improved large airplane configuration having increased seating capacity relative to a single deck configuration, without an excessively long fuselage body and without incurring the evacuation challenges or performance disadvantages of a full upper deck. The present invention is directed to fulfilling this need.